A body-insertable apparatus for taking in body fluid of a patient has been proposed. Specifically, the body-insertable apparatus has a configuration having a capsule-shaped sheathing case, a storage chamber arranged in the sheathing case and having the function of being communicated with the outside of the body-insertable apparatus and of storing body fluid, and a taking control mechanism controlling taking fluid in the storage chamber, wherein the taking control mechanism performs predetermined control upon reaching a predetermined position in a body such as a patient to take in body fluid so that the taken body fluid is stored in the storage chamber.
A conventional body-insertable apparatus has a configuration in which in order to generate a suction force for taking in body fluid, a negative pressure is generated by abruptly changing the volume of a storage chamber with the action of a spring member. Specifically, the conventional body-insertable apparatus incorporates a piston which functions as part of the outer wall portion (a member defining the outer circumference of a region holding a stored target) of the storage chamber, is supplied with a resilient force by a predetermined spring member in the direction in which the volume of the storage chamber is increased, and is supplied with a tension canceling the resilient force by a predetermined fixed string. In such configuration, the piston provided in the body-insertable apparatus is moved according to the resilient force supplied by the spring member when the fixed string is cut based on the function of the taking control mechanism. The volume of the storage chamber is increased with the movement of the spring member to generate a negative pressure in the storage chamber. A suction force is generated so that the body fluid or the like of a body is flowed into the storage chamber (for instance, see Japanese Patent Laid-Open Application No. H02-36848).
A body-insertable apparatus which directly supplies medication to an affected portion in a body by application of the above mechanism has been also proposed. Such body-insertable apparatus according to the above configuration employs a configuration in which medication is previously held in a storage chamber and a spring member supplies a resilient force in the direction in which the volume of the storage chamber is decreased. The resilient force of the spring member acts on a piston by cutting a fixed string. The medication held in the storage chamber is discharged with decrease in the volume of the storage chamber.
The conventional body-insertable apparatus must have the spring member for changing the volume of the storage chamber and has the problem of making the body-insertable apparatus larger. Such problem will be described below.
The body-insertable apparatus of the configuration having the spring member must secure a region housing the spring member therein. To minimize such region, a general body-insertable apparatus employs a configuration in which the spring member is held in the most compressed state before performing a body fluid taking or a medication discharging. The general spring member has the maximum compressibility of only about 70%. A region of at least about 30% of the entire length of the spring member must be secured for housing the spring member. The body-insertable apparatus having the spring member increases the volume by the region housing the spring member. The load of a body into which the apparatus is introduced becomes larger.
The present invention has been made in view of the above and an object of the present invention is to realize a body-insertable apparatus which can make the volume smaller by simplifying a mechanism taking in or discharging predetermined fluid.